Acrylic monomers and the preparation thereof



trite States atent Ofiice J nan Patented Mar. 13, 1962 3,025,319 ACRYLIC MNOMER AND THE PREPARATEON THEREQF Richard D. Anderson, Greenwich, and Edwin Marvin Smolin, Springdale, Conn, assignors to American Cyanamid Company, New York, N.Y., a corporation of Maine No Drawing. Filed Nov. 26, 1958, er. No. 776,405 8 Claims. (Cl. 260-486) This invention relates to a novel method for preparing acrylic esters. More particularly, the invention relates to an improvement in nickel salt-catalyzed, liquid-phase reactions at elevated temperatures and pressures of equivalent amounts of acetylene, carbon monoxide and an alcohol.

The prior art has been plagued by the fact that reactions of the type contemplated herein using nickel salts have not permitted substantial recovery of the nickel catalyst. characteristically, the nickel catalysts heretofore employed, such as nickel halides, nickel sulfides, nickel thiocyanates, and/or their complexes form insoluble basic salts during reaction. More often than not, also, the nickel salt catalyst is converted to a basic nickel salt which acts to polymerize acetylene and acrylate esters. A still further typical drawback is the fact that the nickel catalysts previously employed formed insoluble basic nickel salts which were generally catalytically inactive.

According to the present invention, however, the difficulties heretofore encountered have been substantially mitigated and, in most cases, virtually eliminated. The instant discovery provides a process in which substantially complete nickel catalyst recovery is experienced and the formation of insoluble basic nickel salts is practically eliminated.

Pursuant to the instant invention, equivalent amounts of acetylene, carbon monoxide and an alcohol are reacted in the liquid phase at elevated temperatures and pressures in the presence of a nickel sulfonate catalyst corresponding to the formula wherein x is a value from to 20; and A represents an alkyl group having 1 to 18 carbon atoms, preferably C to C an alkyl-substituted alkyl group having 1 to 18 carbon atoms, preferably C to C said alkyl substituent having 1 to 8 carbon atoms; an unsubstituted aryl group, such as mononuclear and polynuclear aryl groups; an alkyl-substituted aryl group, said alkyl substituent having from 1 to 18 carbon atoms, preferably C to C an alkylsubstituted aryl group of the type just mentioned in which the alkyl substituent having 1 to 18 carbon atoms is, in turn, substituted with a member selected from the group consisting of C to C alkyl groups, an aryl group, an alkaryl group having 1 to 18 carbon atoms in the alkyl moiety, and an aralkyl group having 1 to 18 carbon atoms in the alkyl moiety.

Typical catalysts suitable for the present discovery are nickel methane sulfonate, nickel ethane sulfonate, nickel hexane sul-fonate, nickel para-toluene sulfonate, nickel decylbenzene sulfcnate, nickel benzene sulfonate, nickel isopropyl benzene sulfonate, nickel Z-naphthalene sulfonate, nickel do-decylbenzene sulfonate, nickel bis(2,2- ditolybutane)sulfonate, nickel bis(2,2-diphenylbutane) sulfonate, nickel bis(1,1-dixylylethane)sulfonate, and the like, and mixtures thereof. Generally, up to about 10 percent by weight of nickel sulfonate catalyst, basis the total weight of the non-gaseou reaction mixture, preferably from about 0.30 to about percent, is provided.

By the expression non-gaseous reaction mixture used herein, the non-gaseous components charged to the reactor, i.e., the solvent, alcohol and catalyst, are intended.

concomitantly an alkyl-substituted pyridine or alkylsubstituted quinoline base, and mixtures thereof, can be used. Illustrative of these are: alpha methyl pyridine (alpha picoline), beta picoline, gamma picoline, alpha methyl quinoline (alpha quinaldine), 2-methyl-5-ethyl pyridine (alpha collidine), alpha propyl pyridine, alphan-butyl pyridine and mixtures thereof. The quantity of latter base required for reaction is relatively small. Amounts in the range of about 0.05 to about 5.0 percent by weight, based upon the total weight of the non-gaseous reaction mixture, are satisfactory. In general, a preferred practice is to employ the base in amounts ranging from 0.3 to about 3.0 percent by weight.

While an equimolar ratio of acetylene to carbon monoxide is generally used, the instant invention contemplates the use of an excess of either of these reactants up to about molar percent or more. The use of an acetylene excess in the range of 5 to 50 molar percent is advantageous in that it enhances the rate of reaction substantially without producing tarry by-products.

The alcohol component contemplated herein, such as butanol, propanol, octanol, isobutanol, methanol, isopropanel, lauryl alcohol, oleyl alcohol, and the like, may be present in an equivalent amount basis the acetylene and carbon monoxide reactants. However, an excess of the alcohol is sometimes desirable.

More commonly, however, the gaseous components, acetylene and carbon monoxide, are used in excess over the alcohol when the alcohol is not the solvent, which it Well may be as will be seen hereinafter. An excess of acetylene and/or carbon monoxide over alcohol of 10 to 20 molar percent, or more, for example, is often desirable. Of course, very. substantial excess of the alco- 1101 are employed when the alcohol is the solvent.

While the primary and secondary aliphatic monohydric alcohols just mentioned are commonly used, according to the present discovery, any primary and secondary alco- 1101, including polyhydric alcohols, may be employed. Typical of these polyhydric alcohols are ethylene glycol, propylene glycol, glycerine, pentaerythn'tol, and the like.

Other solvents which can be used for the instant discovery are inert, oxygen-containing, organic solvents, such as tetrahydrofuran, acetone, diethyl C-arbitol dioxane, and the like. Furthermore, the process may be conducted in a batch, semicontinuous and continuous manner.

The reactions contemplat d herein advantageously may be conducted at temperatures a low as C. and as high as 220 C. Preferably, reaction temperatures in the range of about C. to about 205 C. are employed. On the other hand, pressures as low as 200 pounds per square inch and as high as about 900 pounds per square inch are suitable; yet pressures in the range of about 300 pounds per square inch gauge to 840 pounds per square inch gauge are preferred.

As is Well known, the acrylic esters produced by the novel process of the present invention are very desirable materials of commerce. For example, their use in prosthetic surgery, electrical insulation, etc. is very extensive. Consequently, preparation of these materials by a suitable economical and trouble-free process has been the object of research for many years. Peculiarly enough, as indicated above, loss of catalyst has been a source of great anxiety and heretofore a wholly satisfactory solution to the problem had not been found.

The catalysts of the present invention may be prepared as shown by the following typical process:

EXAMPLE A To 13.5 parts of para-toluene sulfonic acid dissolved in water is added sufiicient aqueous barium hydroxide solution to exactly neutralize the acid. To the resulting solution 9.3 parts of NiSO -6H O dissolved in water is added. Barium sulfate precipitates and is removed by filtration, the filtrate being then dried by heating at a temperature of about 100 C. on a steam bath for a period of about 16 hours. A yield of 16.2 parts by weight of the hydrated nickel salt of para-toluene sulfonic acid (90 percent by weight of theory) is recovered, the salt having the formula Ni o n s o 3) Tango The above procedure is illustrative but not restrictive. For example, in some cases the barium salt of the sulfonic acid may be insoluble in this solution; the nickel salt is then prepared by treating the sulfonic acid with nickel carbonate. The elimination of carbon dioxide then yields the desired nickel salt.

Unless otherwise indicated the amounts given herein are in parts by weight.

The present invention will best be understood by reference to the following detailed illustrative examples:

EXAMPLE 1 A charge of 123 parts of a normal butanol solution containing 1.2 parts of nickel para-toluene sulfonate catalyst obtained in the manner described in Example A, above, and 0.5 part of hydroquinone is placed in a rocking autoclave. The autoclave is evacuated with a water aspirator and purged three times with nitrogen. It is then heated to 200 C. with rocking and a mixture which comprises 2 parts of acetylene by volume and 1 part of carbon monoxide by volume is added thereto to create on the reaction mixture a total pressure of 450 pounds per square inch gauge.

In the course of 27 minutes the total pressure drops to 240 pounds per square inch gauge and the mixture is recharged with equal volumes of carbon monoxide and acetylene sufficient to raise the total pressure on the mixture to about 450 pounds per square inch. This process of recharging to a pressure of about 450 pounds per square inch is done eleven times, i.e., at the end of 27, 40, 61, 81, 103, 115, 145, 170, 195, 215, 251 minutes, respectively.

The autoclave is then cooled to ambient temperature (21 C.23 C.) and the product solution removed therefrom. It is analyzed for soluble nickel and found to contain substantially all of the nickel charged in its original form. There is no precipitate. A portion of the solution is distilled at reduced pressure (50 millimeters pressure) and the distillate analyzed for butyl acrylate by quantitative hydrogenation to determine the double bond content. It contains 17.4 parts of normal butyl acrylate per hundred parts of solution.

EXAMPLE II In 150 parts of normal butanol in a rocking autoclave is dissolved 2.26 parts of nickel decylbenzene sulfonate, 1.116 parts of alpha-picoline and 0.123 part of hydroquinone. The resulting solution is heated to 180 C., after evacuating it with a water aspirator and flushing it three times with nitrogen. The autoclave is then charged with equal volumes of acetylene and carbon monoxide sufiicient to create a total pressure in the autoclave of about 485 pounds per square inch gauge. When the total pressure of the autoclave has fallen, through reaction, from 485 pounds per square inch gauge to 461 pounds per square inch gauge, the autoclave is vented to a total pressure of about pounds per square inch gauge. The temperature is then raised to about 200 C. and the pressure raised to a total of about 455 pounds per square inch gauge by the addition thereto of a sufficient amount of acetylene and carbon monoxide, these gases being added in equal amounts by volume.

Next, the autoclave and reaction mixture are rocked for about 50 minutes, at which time the total pressure in the autoclave is about 250 pounds per square inch gauge.

The reaction mixture is then removed from the autoclave and analyzed. It contains in original form 86 percent by weight of the nickel catalyst charged thereto. Butyl acrylate constitutes about 5.5 percent by weight of the product solution.

EXAMPLE III One hundred and fifty parts of normal butanol containing 1.36 parts of Ni(O SCH -5H O, 1.116 parts of alpha-picoline and 0.123 part of hydroquinone inhibitor in a stainless steel autoclave is purged with nitrogen, evacuated with a water aspirator and heated to 200 C. At this point, the total pressure on the mixture is pounds per square inch gauge. Pure acetylene is added to the mixture until the total pressure is 320 pounds per square inch gauge, then pure carbon monoxide is introduced until the total pressure rises to 470 pounds per square inch gauge. The resulting reaction mixture is rocked, the pressure drops to 340 pounds per square inch gauge at the end of 44 minutes and the system is immediately repressured to 410 pounds per square inch gauge by the addition of equal amounts by volume of acetylene and carbon monoxide. The repressuring cycles are represented by the following table:

Table I Pressure Rcprcssurcrl Time drops to to (pounds (minutes) (pounds per per square square inch inch gauge) gauge) One hundred and fifty parts of normal butanol containing 3.26 parts of the nickel salt of 2-tolyl-2-(tolyl sulfonic acid)butane C H 0 II;

1.116 parts of alpha-picoline, and 0.123 part of hydroquinone inhibitor in a stainless steel autoclave is purged with nitrogen, evacuated with a water aspirator and heated to 200 C. The total pressure on the mixture, at this point, is about 180 pounds per square inch gauge. lZli volumes of carbon monoxide and acetylene are sh'HzO then added until the total pressure on the mixture is 470 pounds per square inch gauge.

The reaction mixture is rocked and periodically repressured as shown in the above examples to produce butyl acrylate. Also, as in the above examples, over 85 percent of the nickel hydrocarbon sulfonate originally charged to this system is recovered. Also, a desirable yield of butyl acrylate is recovered.

EXAMPLE V A charge of 150 parts of normal butanol containing 2.372 parts of nickel naphthalene sulfonate 1.116 parts of alpha-picoline and 0.123 part of hydroquinone inhibitor is introduced to a stainless steel autoclave, the autoclave being then evacuated with a water aspirat-or and purged three times with nitrogen. The mixture is heated to 180 0., charged with equal volumes of acetylene and carbon monoxide suflicient to create a total pressure on the resulting mixture of 485 pounds per square inch gauge. The reaction mixture is rocked and, when the pressure on the mixture or system drops to 430 pounds per square inch gauge, the autoclave is vented until a total pressure of 100 pounds per square inch gauge remains. Subsequently, the mixture having a total pressure of 100 pounds per square inch gauge is heated to 200 C. and repressured to a total pressure of 470 pounds per square inch gauge with equal volumes of acetylene and carbon monoxide. Thirty-two minutes later the pressure has dropped to 320 pounds per square inch gauge and, in the manner just shown, the system is repressured to 440 pounds per square inch gauge using equal volumes of acetylene and carbon monoxide.

The system of repressuring is followed several more times at the following intervals:

Table 11 Pressure Repressured Time drops to to (pounds (minutes) (pounds per per square square inch inch gauge) gauge) One hundred and fifty parts of normal butanol containing 1.116 parts of alpha-picoline, 0.123 part of hydroquinone inhibitor and 2.651 parts of mixed nickel dodecyl sulfonates (C H hydrocarbon fraction having a boiling point of 200 C.-214 C.) prepared in the manner shown in Example A, above, from a commercial mixture of the corresponding sulfonic acids, is introduced into a stainless steel autoclave, purged three times with nitrogen, evacuated with a water aspirator and heated to about 200 C. Pure acetylene is then added until the total pressure on the reaction mixture is 320 pounds per square inch gauge; subsequently, pure carbon monoxide is introduced until the total pressure on the mixture reaches 470 pounds per square inch gauge.

In the manner taught in the above examples, the mixture is rocked and periodically repressured to about 440 pounds per square inch gauge until a pressure drop of only about 75 pounds per square inch gauge per 20- minute period is observed. The autoclave and reaction mixture are cooled to ambient temperature (21 C. to 23 C.) and the product solution removed therefrom. This solution is analyzed for soluble nickel catalysts and found to contain over percent by weight of the nickel hydrocarbon sulfonate originally charged to the reactor, the catalyst being in substantially unchanged form.

While the present invention has been described in detail as to specific embodiments thereof, it is not intended that these details constitute undue limitations upon the scope of the invention, excepting, of course, insofar as these limitations appear in the appended claims.

We claim:

1. A process for preparing an acrylic ester by reacting equivalent amounts of acetylene, carbon monoxide and an alcohol in the liquid phase at an elevated temperature and pressure in the presence of a catalyst, the improvement therein of employing as said catalyst a nickel sulfonate corresponding to the formula Ni(O SA) 'xH O wherein x is a value from 0 to 20; and A represents a hydrocarbyl radical selected from the group consisting of alkyl; unsubstituted aryl; aralkyl; alkaryl; and aralkaryl, the alkyl moiety of each of said alkyl, aralkyl, alkaryl and aralkaryl groups having 1 to 18 carbon atoms.

2. The process of claim 1 wherein the catalyst is nickel para-toluene sulfonate having the formula nnomQ-smmmo 3. The process of claim 1 wherein the catalyst is nickel methane sulfonate having the formula Ni (Sor- )MZHQO 5. The process of claim 1 wherein the catalyst is nickel decylbenzene sulfonate having the formula 6. The process of claim 1 wherein the catalyst is the nickel salt of 2-tolyl-2-(tolyl sulfonic acid)butane having the formula (Em NKQoQSOm-mm C2H5 on. on.

7. The process of claim 1 wherein the catalyst is present in the amount up to about 10 percent by weight, basis the total weight of the non-gaseous reaction mixture.

8. The process of claim 1 wherein the catalyst is present in the amount from about 0.3 to about 5 percent by weight, basis the total weight of the non-gaseous reaction mixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,806,040 Reppe et a1. Sept. 10, 1957 09,976 Reppe et al. Oct. 15, 1957 2,845,451 Lautenschlager et al July 29, 1958 FOREIGN PATENTS 859,612 Germany Dec. 15, 1952 

1. A PROCESS FOR PREPARING AN ACRYLIC ESTER BY REACTING EQUIVALENT AMOUNTS OF ACETYLENE, CARBON MONOXIDE AND AN ALCOHOL IN THE LIQUID PHASE AT AN ELEVATED TEMPERATURE AND PRESSURE IN THE PRESENCE OF A CATALYST, THE IMPROVEMENT THEREIN OF EMPOLYING AS SAID CATALYST A NICKEL SULFONATE CORRESPONDING TO THE FORMULA 